This invention relates generally to pneumatic devices for firing a projectile, and more specifically, to a pneumatic device that discharges compressed air behind a projectile to accelerate the projectile down and out of a barrel.
Pneumatic or pressurized gas-actuated devices for firing various shaped and sized projectiles are known in the art. These devices are commonly used to propel appropriate sports balls in practice activities for various sports, such as baseball and tennis, although a more common mechanism for propelling practice balls employs friction between a ball and a rotating wheel. Other pneumatic projectile firing devices have been developed for sports such as paintball, where participants engage in mock battles and fire pellets of colored liquid at one another. Still other pneumatic devices, such as B-B guns or pellet guns, are designed for firing small caliber projectiles for target shooting or small game hunting. A very wide variety of different-sized projectiles can be fired with a pneumatic device, and in each of these prior art devices, the projectile being propelled through a barrel is sized to maintain a relatively close fit between the projectile and the bore of the barrel to minimize loss of pressure and reduced efficiency.
A common characteristic of these prior art pneumatic devices is that the size or caliber of the projectile that is pneumatically propelled is thus directly linked to the diameter of the barrel of the device. Consequently, only one size or caliber of projectile can be used with a particular barrel. A tennis ball can therefore not be used with a prior art pneumatic pitching machine that is designed to propel a softball because the sizes of the two different types of ball are so disparate. Furthermore, a projectile that is substantially smaller in diameter than the barrel can randomly strike the sides of the barrel while being accelerated, which will likely adversely affect the accuracy of the projectile""s accuracy and may result in damage to the barrel or to the projectile.
An apparent solution to the problem of propelling different diameter projectiles with the same pneumatic device is to provide interchangeable barrels of corresponding different diameters, so that more than one size of projectile can be fired by the same device. However, this solution is not entirely satisfactory, because the barrel of a pneumatic device represents a significant portion of the entire device, and changing barrels is not such a simple task as to be convenient. It would be desirable to develop a device that is capable of firing more than one size of projectile using a single barrel, and without causing damage to the barrel or reducing the accuracy of the projectile""s aim.
As mentioned above, prior art pneumatic devices have been used to propel balls with a desired trajectory and velocity for practice activities relating to such sports as baseball and tennis. For example, U.S. Pat. Nos. 4,524,749; 4,834,060; 4,995,371; and 5,121,735 disclose automatic pitching devices that forcibly eject baseballs to enable a person to practice batting the ejected baseballs. Such devices require a barrel specifically designed for a single type of ball, either a baseball, a softball, or a practice ball. A practice ball is the same general size and weight as a baseball, but lacks the stitched seams of a baseball. Some prior art pitching machines, particularly non-pneumatic pitching machines that propel a ball using one or more rotating wheels, do not function well with actual baseballs, because the stitching orientation can change randomly from one ball to the next. The pitching machine wheels may engage the balls differently on successive pitches, adversely affecting the accuracy of successive pitches. Thus practice balls have been developed for use with such devices. In the prior art, a separate device, or at least a separate barrel, has been required for projecting tennis balls, baseballs, and practice balls, even though the relative sizes (diameters) of all three types are similar.
While many of the prior art devices, including non-pneumatic devices, for imparting a desired trajectory to a spoils ball function in a generally satisfactory manner for a particular type of ball, room for improvement in the art still exists. It would be desirable to develop a device for use in pitching balls that has certain desirable features, such as a size and weight sufficiently limited so the device is readily portable and can be transported and set up by a single person, using a portable power source. This device should also have a relatively low cost and should incorporate certain safety features. For example, an enclosure should be provided for moving parts to prevent accidental injury to fingers that might otherwise be caught in the mechanism. A lockout mechanism should be included to prevent a projectile from being fired if an object or individual is blocking the mouth of the barrel. An audible/visual warning should be provided just prior to a projectile being launched. Further desirable features for this type of device, which will appeal to baseball players in particular, would be a display of ball speed, and the ability to deliver projectiles with relatively high accuracy and consistency, in a relatively fast cycle. It would be further desirable to develop a device that is capable of firing objects that are irregular in shape and do not closely conform to a cross-sectional shape of a barrel.
In accord with the present invention, a device is defined for ejecting a projectile from a barrel using a projectile carrier that when acted upon by a charge of compressed fluid, propels the projectile through the barrel. The barrel defines an inner space and has an open end and a closed end. The projectile carrier is disposed at a firing position within the barrel, generally adjacent to the closed end and is sized to move freely within the barrel. When acted upon by the charge of compressed fluid, the projectile carrier transfers kinetic energy to a projectile and ejects the projectile from the barrel along the desired trajectory.
Preferably, the barrel is of sufficient length so that as the pressure within the barrel drops to a level below ambient air pressure due to the forward motion of the projectile carrier through the barrel, the projectile carrier is prevented from being ejected from the open end of the barrel.
The device also includes a chamber that holds the charge of compressed fluid and a valve that controls the release of the charge of compressed fluid into the barrel behind the projectile carrier. The chamber is coupled in fluid communication with the inner space of the barrel through the valve. When the valve opens, the pressure of the compressed fluid imparts kinetic energy to the projectile carrier. The pressure of the charge of compressed fluid in the chamber is selectively variable, and the velocity of the projectile can be controlled as a function of the pressure in the chamber. The valve is electromagnetically actuated.
In one preferred embodiment, the device includes a rechargeable battery. Further, an external power source or the battery can be selectively chosen to provide an electrical current to energize the device.
A microprocessor is preferably included in a controller to determine a magnitude of pressure developed in the chamber, and thus to achieve a desired velocity. The microprocessor is electrically coupled to the compressor, the valve, a display, and a control panel and implements a firing sequence. The microprocessor prevents the device from being operated until a correct password has been entered into the control panel.
An optical sensor disposed adjacent to the open end of the barrel is electrically coupled to the microprocessor. The optical sensor detects the ejection of a projectile from the barrel, and the microprocessor determines the velocity of the projectile and indicates the velocity on the display. Preferably, the microprocessor prevents the release of the charge of compressed fluid if the optical sensor indicates the presence of an object at the open end of the barrel, thereby preventing a projectile from being ejected when the open end of the barrel is obstructed. Furthermore, the microprocessor initiates a firing sequence when the optical sensor detects a projectile being loaded into the open end of the barrel.
A key feature of the device is the projectile carrier. Preferably, the projectile carrier includes a surface shaped to center the projectile within the barrel during the acceleration of the projectile through the barrel, thereby minimizing random contacts between the projectile and the interior surface of the barrel. This surface is shaped to accommodate different size projectiles, so that the different size projectiles can be ejected using the same barrel.
Another aspect of the present invention is directed to a method that includes steps generally consistent with the description of the apparatus set forth above.